While I'm sure I don't have a grasp of "the big picture", I would have imagines these would have acted like a mask against the file system attributes. In effect setting O_RDONLY would clear the write permission bits read by stat(), and O_WRONLY would clear the read permission bits. O_RDONLY + O_WRONLY (O_RDWR) would leave the permissions alone. These would be applied somewhere around the may_open() call in fs/open_namei.c

A poor mans umaks(), I guess.

--John

On Saturday 12 July 2003 01:11 am, Valdis.Kletnieks@vt.edu wrote:> On Fri, 11 Jul 2003 20:38:09 PDT, Andrew Morton said:> > "J.C. Wren" <jcwren@jcwren.com> wrote:> > > I was playing around today and found that if an existing file is opened> > > wit>> h>> > > O_TRUNC | O_RDONLY, the existing file is truncated.> >> > Well that's fairly idiotic, isn't it?>> Not idiotic at all, and even if it was, it's still contrary to specific> language in the manpage.>> I could *easily* see some program having a line of code:>> if (do_ro_testing) openflags |= O_RDONLY;>> I'd not be surprised if J.C. was playing around because a file unexpectedly> shrank to zero size because of code like this. There's a LOT of programs> that implement some sort of "don't really do it" option, from "/bin/bash> -n" to "cdrecord -dummy". So you do something like the above to make your> file R/O - and O_TRUNC *STILL* zaps the file, in *direct violation* of the> language in the manpage.>> Whoops. Ouch. Where's the backup tapes?>> > The Open Group go on to say "The result of using O_TRUNC with O_RDONLY is> > undefined" which is also rather silly.> >> > I'd be inclined to leave it as-is, really.>> I hate to think how many programmers are relying on the *documented*> behavior to prevent data loss during debugging/test runs....>> /Valdis